Since Danger Mouse (DM) is SUPER CHEVY's in-house test engine and we vowed long ago to test any combinations suggested to us, this month is our first example of mixing the wrong components. The culprit here is not a bad part. Rather, the culprit is the improper selection of a combination of parts. Last month, we said we'd swap cylinder heads to see if the stock GM camel hump castings were keeping DM from making more power. Since the inception of DM, we've received many letters from readers suggesting we equip it with a set of World Products S/R Torquer cylinder heads to help out in the horsepower arena. We did just that but did not make any other adjustments in conjunction with the new heads. As with any swap you make, how your upgrades work with each other is the determining factor in whether or not your "better" part is actually "better" for your current setup (or whether you'll need to make some adjustments in order to use your better part). The root of the power loss we suffered came from the fact that the S/R Torquer heads (S/R stands for "stock replacement") were bigger than the stock GM heads in all the critical areas. And on a low-rpm street motor like DM, bigger is not better. The S/Rs had larger combustion chambers (67 cc vs. 62 cc on the milled 461 castings we'd been running) and larger valves (2.02/1.60 vs. 1.94/1.50). The large combustion chamber dropped Danger Mouse's compression ratio 1/2 point, putting it just below the 9:1 mark, and the larger valve sizes, particularly on the intake side, probably reduced charge velocity enough to hamper the cylinder's filling at low speeds.

3/13

Improper cylinder head selection resulted in less power and torque. Although the net result of our test wasn't a horsepower gain, it proved a positive lesson in choosing the correct parts.

What We LearnedAll this month's test proved is that it's extremely critical to know exactly what parts you have before you start replacing them. That might mean having your car sit in the garage for a few days while you remove the heads and measure everything prior to ordering the new parts. But that's the only way to be sure you won't be taking a step in the wrong direction. Had DM originally been equipped with a set of heads that had big 76cc chambers, the S/R heads would have boosted compression and that would have probably made more power. Also, if DM was a higher-rpm engine or had more cubic inches, ala stroker 383, it could have made good use of the S/R's larger valves as well. Even though we know we could mill the S/R heads to get an equal compression ratio and re-test them to see the results, we'd rather not start modifying parts this early. Instead, we'll box up the S/R heads and re-test them again another time when DM's got either more inches or more rpm to play with.

12/13

Last Month's Power RecapIn DM's third bash on the dyno we really started to crank out some power, especially considering that DM still wore its stock iron heads and had a mild hydraulic camshaft. DM ended the day with a maximum 386 hp and 438 lb-ft of torque. The average horsepower and torque figures were 316 and 416, respectively (see: Test 12). That was 30 hp and 25 lb-ft more torque than we'd started the day with. Needless to say, we were very impressed with the results.

However, this month, for DM's fourth dyno test, we thought we could do a little better by replacing the stock heads, so we tried a set of S/R Torquers (which we got from Bill Mitchell's Hardcore Racing Products for $415 each) and were taught a lesson in proper parts matching.

13/13

4th Series Of Dyno TestsWe'll number every series of tests consecutively, starting with the last number of the previous month's tests. We'll also list the last test from the previous month so you'll have something to compare the new tests to. So this month our first new test is number 13. Unless listed, no other changes were made for any test.

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